Process for converting hydrocarbons



zm. 959 E935. F. E. FREY 399579997 PROCESS FR CONVERTING HYDROCARBONS Filed Nov. 2 2, 1932 rWC/Yw J7.' E. @may Patented Jan. s, 1935 stars esito? @GNVERTING HYDRO- QQNS f @ses rees, ru e -f Petroleum v Company, time., a corporation oi Delaware Philiips e, Ghia.. assigner to Bartlesville,

duplication Novemlier 22, i932, Serial No. 643,919

Z whims. (Cl. X36-10) This invention relates to a process for the conversion of hydrocarbon gases into valuable normally liquid hydrocarbons by heating to a reaction temperature under high pressure.

s It has been proposed to convert gaseous olenes, namely ethylene, propylene, and the butylenes into oils by heating under a pressure in excess of 500 pounds per square inch to a temperature oi r'00 to l00 F., whereupon polymerization takes l0 place and volatile normally liquid hydrocarbons are produced. It has been shown that the velocity of the polymerization reactions is greatly increased byincrease in pressure, the formation of oils taking place rapidly, under partial pressures l5 of olene exceeding 500 pounds per square inch,

at temperatures of '10D-850 F. at which the crack ingof gaseous parans is very slow.

It has further been proposed to convert 'the gaseous params which are more refractory than 2o oleflnes into normally liquid hydrocarbons by heating to a cracking temperature above 750 F.

under a pressure of 500 or more pounds per squarev inch to edect a conversion into normally liquid hydrocarbons. When operating at elevated pres 2o sures I have found that, owing to the high tem# peratures required to eect an initial cracking of the gaseous paramns to. produce olenes, only a partial conversion into normally liquid hydro@ carbons can se effected by a single exposure to a Sli conversion temperature without the formation of tar and carbon, a great part of `the parains surviving the conversion operationunchanged.

The object of the present invention is to increase the yield 'of normally 'liquid hydrocarbons $5 obtainable from gaseous hydrocarbons in a single passage through the conversion unit, thereby in# j creasing the emciency of the process.

A further object is to convert olenic hydrw carbons other than those formed in the converd@ sion sone into anadditional yield ci liquid hydro- Y carbons.- Y `Further objects will be apparent as the disclosure pr. 1

' When ethane, propane, or butano is heated to ed a cracking temperatur-eo! E50-100 F; decomposition take's place and smaller molecules, chiefly of the gaseous olefines, are produced. if the decomposition takes piace under high pressure,v the oleilnes areiorrned in high concentration and 50 'their polymerization into oils takes place rapidly, mst .with the formation oi volatile oils, and, as the reaction proceeds, with the subsequent formation of heavy oils and carbon.- The formation of heavy oils and carbon' necessitates arresting 55 the crackingbefore they are formed in suicient amounts to interfere with the economical operation of the process. Even in the conversion of hutanes into oils the initial decomposition proceeds so much more slowly than the subsequent reactions under pressures in excess of 1000 pounds 5 per square inch that the greater part of the butane must be discharged from the reaction zone unchanged, accompanied by about 8-14 percent ci higher boiling hydrocarbons, as Well as similar amounts of the other gaseous paraillns and gasel0 ous olenes. The primary decomposition of propane takes place at approximately one-third the rate of the butanes, and the conversion into loils is accordingly much less. Ethane yields even less oil than propane, while methane is substani5 tially inert.

in the neighborhood of 1000s F. the rate of primary decomposition of propane and butane is 'increased approximately-fold by an increase in temperature oi 50 F., while the rate ci. conversion 20 into oils o the olens produced by the aforesaid primary decomposition I have found to be increased approximately Z-fold by a 50 F. increase in temperature. Consequently, the velocity ofthe `primary decomposition relative to the oil 25 forming reactions is increased with increase in temperature, and l2 have found that, at the more elevated temperatures, an increased decomposition of parains may be obtained in a single exposure to a decomposition temperature before 30 the conversion need be interrupted by reason of tar and carbon-formation, and temperatures in escess ci i000" F., usually considered prohibitive in pressure cracking, give the best results.

The conversion oi gaseous 'olenes into oils 35 involves asequence ci changes into volatile oils, heavy oils, and dnally carbon. over the rather Wide temperature range'oi '100 to 1500 F. or higher, but the nature of the oils formed is affected/by vthe reaction 'to a marked degree. 40 At the lower temperatures, '700 to 800 F., and

elevated pressure, thel aliphatic and alicyclic oils,

I have found, arev virtually the sole products oi the polymerization, while at higher temperatures, oils of higher carbon vcontent are formed, together with additional methane, the oils being largely aromatic when formed above 1200 'il'.I The formation 'of aromatics and additional methane entails a loss in yield of oils-at the higher temperatures, and the lower range of polymerization temperatures are accordingly to be preferred when a maximum yield is desired.

The present process achieves an increased yield of oils per pass through a coil by exposing gaseous parafllns under high pressure to a high reaction temperature, preferably 1050-1250 F., for a time suiliciently long to effect a maximum decomposition into smaller molecules together with oils, but not long enoughl to permit excessive carbon and tar formation, then maintain-k ing vthe reaction products, still under pressure, and at a polymerization temperature lower than the decomposition temperature for a time sufficient to effect a substantial further conversion into oils, chiefly aliphatic and alicyclic, at the lower polymerization temperatures.

An apparatus suitable for use in practicing lthe process is diagrammatically illustrated in the accompanying drawing, which shows a side elevation of a suitable apparatus.

I n practicing the invention, normally gaseous hydrocarbons consisting chiefly of butanes, enterl pipe A under a pressure of 1000-5000 pounds per square inch and pass continuously and at a high velocity through tube coil 'B of restricted cross-sectional area situated within furnace housing C whereinethe hydrocarbons are heated to a reaction temperature preferably within the range 1050-1250 F. 'Ihe hydrocarbons crack endothermally and, upon exposure to cracking temperature for a time sufficient to produce a high content of lower paraffins and olefines as v.wellas oils, are discharged from coil B and may be partially cooled either by loss of heat or by the introduction throughD of hydrocarbons at a lower temperature. The hydrocarbon is then exposed in reaction coil E, without any substantial further introduction of heat, to a'polymerization temperature for a time suilicient 'to produce an additional yield of oils by polymerization of gaseous oleiines. The reaction product containing oils and unchanged charging stock aswell as lower gaseous hydrocarbons passesinto a-partial condenser F wherein a part of the butanes and*` the higher boiling hydrocarbons are separated and withdrawn at K. The vapors from F pass,

hydrocarbons, (principally ethane and propane),

is released at I. The butanes are particularly suitable for conversion in the process, and the yield of oil is increased by the presence of gaseous oleiines, entering either at A-or D, or both. 'Ihe lower paraflins, particularly methane and ethane, because of-` their high.decompositio'n temperatures, are substantiallyinert in the presence of butanes and olefines, and detract .from the efiiciency of the process. For this reason, only a limited amount of the lower parafdns are Vbest returned with butanes for retreatment, un-

less they are accompanied by substantial proportions of the desirable gaseous oleiines.

Vapors containing substantial amounts of gaseous oleiines are most suitable for introducing at D, particularly a concentrate from cracking still gases containing a large proportion of butylenes and butanes. The olefines are desirable since they enter into reaction rand augment the yield of oils. A high proportion of such vapors can obviously be added if they are preheated to a suitable degree. I'he lower hydrocarbons discharged from J andi are suitable for fuel or other uses; the material from I contains chiefly hydrocarbons higher than methane and is 'suitable for conversion into aromatic oils by cracking at high temperatures.

'I'he endothermic cracking is best conducted at I temperatures within the range 1050 to 1250i li.

short time of exposure which the use of high` temperatures necessitates. Pressures of 1000 to 5000 pounds per square inch or more may be used, but I prefer to use a pressure of Z500-3000 pounds. The lower pressures necessitate the use of high temperatures in the polymerization operation with consequent loss of yield and increased formation of carbon, with the formation of4 oils of higher aromatic content. The duration of the endothermic cracking operationis preferably less than three minutes, but the conditions for con. ducting this operationare better defined by the temperaturel and composition of the issuing products, as set forth, since heat transfer .considerations play a dominating part.

'Ihe polymerization step is preferably carried out at temperatures of from 800 to 1000 F.; the selection of the temperature depending chiefly on the, result desired. The time of residence in the polymerization chamber is usually much greater than that required for the primary'mdecomposition, vin order to permit the optimum conversion into oils at the moderate `tempera.- tures required for developing the best yields of normally liquid hydrocarbons. The residence in 4the polymerization chamber should not be con-v What is claimed and desired to be secured by Letters Patent is:

1. The process for converting hydrocarbon fluids predominantly parafllnic and of three and four carbon atoms per molecule into normally liquid gasoline hydrocarbons, which comprises -to permit substantial carbon and tar formation,

then while maintaining the pressure, passing all the thermally treated fluid without further addition of heat through a zone wherein a reaction temperature below 1000 F. is maintained fora time sufficient to effectA a substantial further Aformation of oils, then cooling the thermally treated hydrocarbons, and nally separating the normally liquid hydrocarbons.

2. 'I'he process for converting hydrocarbon fiuids predominantly paraillnic and of three and four carbonatoms per molecule, into normally liquid gasoline hydrocarbons, which comprisesv i continuously passing such a fluid at a temperature of about 1050-1250 F. and under a pressure of 1000 to 5000 pounds per square inch through a heating zone of restricted cross sectional area and thereby eiecting the conversion of a substantial portion of the fluid into gaseous oleilnes and normally liquid hydrocarbons, then while maintaining the pressure, passing all of the ther-i mally treated fluid without further addition of heat through a conversion zone wherein a reaction temperature oi!4 between about 800-1000 F. is maintained for a time sufficient to eiiect a substantial further conversion into oils, then cooling the thermally treated fluid, separating the normally liquid hydrocarbons from the same, also separating from the fluid a condensate of normally gaseous hydrocarbons predominantly of three and four carbon atoms per molecule, and returning said condensate Vto the heating zone.

3. A process for converting hydrocarbon material consisting essentially of propane and/or butane comprising lsubjecting said material to a temperature of about 1050-1250" F. and a pressure of 10004000 pounds per square inch, then admixing all the thermally treated material with hy- -drocarbon material containing a substantial amount of normally gaseous oleilnes, and then subjecting the resultant admixture to a temperature of about 800-1000 E. and a pressure of 1000- 5000 pounds per square inch.

4. A two stage process for the non-catalytic conversion of nornally gaseous paraiiin hydrocarbons infn normally liquid gasoline hydrocarbons comprising'subjecting tbe initial hydroca'rbons,inanrststage,toapressureof.10005000 pounds per square'inch and a temperature above about 1000F., and then subjecting all the maserial from um amature. in a mandame, to s.

prsureof 1000-5000poundsandatemperature subjected to said second stage. l,

' 5. Aprocessfortheconveraionofhydroearbon material consisting principally of butanes and propane into volatile normally liquid gasoline hydrocarbons which comprises subjecting said matermi u a temperature above about 1ooo Runder pressure of 1000 to 5000 pounds per square inch for such a period of time as to permit the formation of olefin hydrocarbons without the forma.-

tion of heavy oils and tare, then passing said ma- 'terial, without substantial reduction in pressure l or separation of any of the reaction products, into .a zone in which the said material is maintained at a temperature below 1000 F. for a period of time suiiicient to polymerize the aforesaid olens into volatile oils.

6. A process for the conversion of hydrocarbon' material consisting principally of butanes and propane into volatile normally liquid gasoline hydrocarbons which comprises subjecting said material to a temperature above about 1000 F. under pressure of 1000 to 5000 pounds per square inch -for such a period of time as to permit the formation of olefin hydrocarbons without the formation of heavy .oils and tars, then passingv said material, without substantial reduction in pressure or separation of any of the reaction products, into a zone in which the said material is maintainedv at a temperature between 800 and 1000 F. for a period of time sufficient to polymerize the aforesaid oleiines into volatile oils.

'1. A process for the conversion of hydrocarbon material consisting principally of butanes and propane into volatile normally liquid" gasoline hydrocarbons which comprises subjecting said material to a temperature above about 1000"y F. under pressure of 1000 to 5000 poundsper squareinchfor suchaperlodoftirneastopermit the formation of oleiin hydrocarbons without the formation of heavy oils and tara, then v 'the' aforesaid oleilnes into volatile oils. v

salamoia. 

